1. Field of the Invention
The present invention relates to a method and to a device for determining the carrier frequency of base stations in the mobile receiver of a cellular mobile radio system working with W-CDMA.
The present invention relates to mobile receivers for cellular mobile radio systems with W-CDMA (wide-band code division multiple access) as described in detail in the literature, for example in P.Jung “Analyse und Entwurf digitaler Mobilfunksysteme” (Analysis and Design of Digital Mobile Radio Systems”, B. G.Täubner-Verlag, Stuttgart, 1997 and in the journal IEEE Transactions on vehicular technology, Vol. 47, No.4 of November 1998 in the article “W-CDMA—The radio interface for future mobile multimedia communications”. This method is of considerable significance because it is intended to form the world-wide standard for the third-generation mobile telephony technology as explained in IEEE Transactions on vehicular technology, Vol. 47, No. 4 of November 1998 in the article “UMTS universal mobile telecommunications system: Development of standards for the third generation”.
In this novel operating method for the mobile telephony, the problem occurs that when the mobile receiver is switched on the first time, it has no information on the frequency and the timing of the transmissions of the surrounding base stations. The mobile receiver, therefore, must perform an initial cell search in order to determine the base station with the strongest received signals and the associated time synchronization of that base station. This task is one of the most difficult and computing-time-consuming tasks for the mobile receiver in a W-CDMA mobile radio system.